Atlanta—The greater availability of flu vaccines, through pharmacies and other convenient outlets, contributed to some good news out of the national Centers for Disease Control and Prevention.

According to CDC calculations, approximately 13 million illnesses and more than 110,000 hospitalizations likely were averted by vaccination against influenza from 2006 to 2011.
The report was published in the open-access journal PLOS ONE.

CDC researchers calculated the health care burden of flu cases that would have occurred in the absence of vaccination, based on factors such as illness and hospitalization rates during the flu season, vaccination coverage, and vaccine effectiveness. The largest number of averted cases occurred during the most recent period studied, 2010 to 2011, when 5 million flu cases, 2.1 million medical visits, and 40,400 hospitalizations were prevented by vaccination, according to the report.

“The increase in the prevented fraction during the 2010–2011 season relative to earlier seasons demonstrates how increases in vaccination coverage can drive substantial improvements in the impact of vaccination,” according to the report. “Likely due to raised post-pandemic awareness about influenza, overall vaccination in 2010–2011 increased compared to both pandemic and pre-pandemic levels. In 2010, a higher proportion of vaccinations also occurred earlier in time than during previous seasons, with relatively higher vaccination rates in the months of August and September. The increases in vaccination coverage across all age groups that occurred in the season after the 2009 pandemic produced the largest vaccine impact observed over the six-year study period both in terms of prevented fraction and number of averted cases.”

The United States is the only country with universal influenza vaccine recommendations, suggesting that everyone 6-months-old or older should receive an annual dose of the vaccine, researchers noted. Previous studies have not provided ways to reliably assess the number of flu cases or hospitalizations that are prevented by vaccination each year, however.

“These results confirm the value of influenza vaccination, but highlight the need for more people to get vaccinated and the imperative for vaccines with greater efficacy, especially in the elderly,” according to
senior author Joseph Bresee, MD.

The report concludes, “Vaccination against influenza has a substantial annual impact on the burden of disease in the United States. The study demonstrates that improvements in vaccination coverage among non-elderly persons and improvements in vaccine effectiveness among the elderly will lead to greater gains in program effectiveness.”